Our best guess comes from religion reporter colleagues who after the Gizmodo reporting found Comey’s undergraduate thesis at the College of William & Mary. The paper was about Niebuhr, a prominent theologian.

Jack Jenkins wrote in Think Progress that while most Americans wouldn’t know Niebuhr’s name today, “he was once unavoidable: beginning in the 1930s and extending into the 1960s, Niebuhr’s various treatises on the intersection of Christianity and public life were at the center of innumerable public debates, and his voice was a constant in conversations about the moral dimensions of war, use of nuclear weapons, and civil rights.”

Among those who have quoted and called Niebuhr their favorite theologian are thinkers and politicians from Barack Obama and Hillary Clinton to David Brooks and John McCain, Jenkins wrote.

In a spring piece in Christianity Today, Steven Weitzman wrote that for leaders across the ideological spectrum, Niebuhr “offers a justification for pragmatism, for the use of force, and for the moral compromises that political action imposes”:

How did this particular theologian become so many politicians’ moral and spiritual compass? Niebuhr developed a view known as Christian realism, believing the human ego would undercut our attempts to better the world. According to Niebuhr, people need to shed their self-righteous illusions and perfectionist pretensions to set their sights on more modest solutions. Niebuhr warned that people should never assume they could eliminate evil. In fact, they should be on guard lest their moral ambitions lead them into a self-deluded and destructive pride.

Comey’s thesis compares Niebuhr with Moral Majority leader Jerry Falwell. At the time, the televangelist had emerged as a central figure in American politics following the election of President Ronald Reagan. Comey’s study was an effort to understand how each man would answer the question: “Why should the Christian be involved in politics?”

Comey, who Jenkins said is a Methodist, in the paper rejects what he sees as Falwell’s “numbers game” approach to Christianity and what he characterizes as a concept of a “Christian America.” Instead, Comey embraces Niebuhr’s version of nationalism, one that “champions a different kind of civic duty, one that requires ‘prophetic’ criticism of leaders and loyalty to the divine over country,” Jenkins summed up.

“For Niebuhr the true prophet is an internationalist who casts all national pretensions in the light of divine judgment,” Comey’s thesis said. “The prophet measures all collective human action against the norm of love, and all groups fail to measure up.”

A New Yorker piece in April by Paul Elie notes that the FBI kept a 600-page file on Niebuhr. The basis was J. Edgar Hoover’s view that “anybody who belonged to so many left-wing organizations had to be a Communist,” the piece quotes a recent documentary about Niebuhr as saying (the documentary is called “An American Conscience” and it came out earlier this year). Elie’s essay considers Comey’s embrace of Niebuhr, someone who often argued against “simple schemes of good and evil.”

“To see Niebuhr’s story with Comey in mind is to gain a deeper appreciation of the hard choices Comey has faced—and the perils of going it alone, as he has seemed to do at several points,” Elie wrote, noting Comey’s decisions related to the cases of Donald Trump and Hillary Clinton.

On Sunday, Comey tweeted a photo of birds, and said he was “thinking about Niebuhr’s Serenity Prayer.” The prayer, which is generally attributed to Niebuhr, is one of the most famous American meditations, adopted by clergy as well as many 12-step programs. It reads: “God, grant me the serenity to accept the things I cannot change, courage to change the things I can and wisdom to know the difference.”

Niebuhr’s vision of Christianity lived out in America — and Comey’s selection of the name — is striking in 2017, when a more Falwellian, America-first Christian nationalism has roared to the fore.

With the rush Monday about Comey confirming he is “Reinhold Niebuhr” (or @FormerBu), there was still almost zero discussion of the theologian whose name the account bears. The chatter in comments and articles was all about Comey’s political future and what he might accomplish now that he’s trying to be in public “in useful ways.” His final tweet read:

Tweeting a copy of the Presidents tax returns would be *super* useful, ya handsome string bean of justice.